Because Internet has good communication capability, mass information storage and acquisition capability, the IP technology, as the supporting technology for constructing Internet, becomes such a common network technology that various related and unrelated networks are to employ IP technology or to be compatible with it. Based on the IP technology, a technology known as mobile IP is proposed to address the need of maintaining service continuity while a mobile node (MN) is in roaming. As Internet develops rapidly, IP addresses are becoming badly needed and will soon be used up. IPv6 is developed on the basis of current IP technology (IPv4) to address this problem; corresponding mobile IP technology also evolves from MIP4 to MIP6 (Mobile IPv6). The fundamental principle of MIP6 is shown in FIG. 1:
(1) An MN operates in the same manner as other fixed nodes when it is connected to its home network.
(2) The MN detects whether it is roaming into a foreign network by the neighbor discovery mechanism of IPv6. Foreign gateways of IPv6 periodically transmit router advertisement messages including the prefix of the foreign network, and after receiving the router advertisement messages from the foreign gateway, the MN determines that it has roamed into a foreign network if it finds that the prefix of the foreign network therein is different from that of the home network.
If the MN finds that it has moved into a foreign network, it acquires a care-of-address in the foreign network through a stateful or stateless automatic address configuration process on the basis of the received router advertisement message. Now the MN has both a home address and a care-of address.
(4) The MN registers its care-of address with a home agent by a “binding update” message.
(5) The MN can also notify its correspondent node (CN) of its care-of address by a “binding update” message registration. Before the registration, a Return Routability Test Procedure should be performed between the MN and the CN, i.e. the MN first sends a Home Init Test message and a Care-of Init Test message to the CN and the CN returns a Home Test message and a Care-of Test message to the MN after processing.
(6) If the CN does not know the care-of address of the MN, it will transmit packets to the MN's home network according to the MN's home address, then the home agent of the MN will intercept the packets and forward the packets to the MN by tunneling mechanism according to current care-of address of the MN.
Packets transmitted to the CN by the MN are also transmitted to the home agent by a reverse tunnel and then forwarded to the CN by the home agent. This is also called a “triangle routing” because all packets transmitted between the CN and the MN need to be forwarded by the home agent in this manner.
(7) If the CN knows the care-of address of the MN through the “binding update”, it will transmit packets directly to the MN by use of a route header of IPv6. Because a first destination address of the packets is the care-of address and a second destination address is the home address, the packets are transmitted directly to the MN in the foreign network without being forwarded by the home agent.
In a reverse direction, packets transmitted by the MN to the CN have the care-of address as the source address and the home address stored in the destination extension header of the packets. Thus, the packets can also be directly transmitted to the CN instead of being transmitted to the home agent through the reverse tunnel. This is called a “route optimization” corresponding to the “triangle route” in (6).
As 2.5G/3G wireless network and broadband IP network are applied popularly, a next generation network (NGN) is proposed, which is expected to be compatible with all existing networks, be capable of carrying all service media, provide good interface and extension capability for new service improvements and ensure ubiquity, security and good quality of service (QoS) of communication.
The fundamental architecture model of the NGN network is shown in FIG. 2 and the entire network model is divided into a service plane and a transmission plane. The transmission plane is subdivided into 4 functional parts: network access control function, resource admission control function, access network function and core transmission function. The network access control function includes an MN database, an authentication and authorization function entity, a network access configuration control function entity and a location management function entity, and the resource admission control function includes a policy determining function entity, an access resource control function entity and a core transmission resource control function entity.
An MN is connected to the NGN network through an access network and controlled by the network access control function. In the network access control function, the authentication and authorization function entity inquires the MN database for authentication and authorization of the MN, and after authentication and authorization of the MN is passed, the network access configuration control entity configures the MN's network characteristics (e.g., IP, DNS, gateway etc.); the location management function entity collects the MN's location information and transmits it to a control entity related to the service plane.
The resource admission control function receives a resource scheduling request from the service plane and resolves the request into access network resource request and core network resource request by the policy determining function entity. The access network resource control entity and the core transmission network resource control entity resolve the respective requests into actual network resources bandwidth representation respectively and deliver them to related entities in the access network and the core network.
The access network and the core network may enable/disable terminal transmission function for MNs after receiving control requests from the network access control function (NACF) and the resource admission control function (RACF).
There is no support for mobility management in the existing NGN architecture model; while the current MIP6 technology is a technology developed mainly for solving mobility issue for Internet and not for broad requirements of hierarchical network such as the NGN network; therefore the existing MIP6 technology has the following disadvantages:
1. Because the control function and the forwarding function are not separated, all packets are processed in one plane, which is not suitable for hierarchical network architecture like the NGN network; and the management pattern and control pattern can not meet requirements of hierarchical network and hence not meet the development trend toward layered management of future network.
2. Lacking the cooperation capability among multiple mobility control agencies, which only satisfies the requirements of local network mobility IP management and does not satisfy requirements of mobility IP management of large complex network.
3. Incompatible with operation mode of MIPv4.
4. Insufficient use of mobility management capability of the network the CN resides and the route optimization manner being unable to ensure the privacy of MN's address.